A Tree is a Sink

Kids love to climb trees. One of the fondest memories of my long-ago childhood is the day I was finally able to pull myself up onto the lowest branch of a towering maple tree in our suburban backyard. Scrambling further on up, I peered through the leafy canopy, out over the rooftops of my neighborhood. There, in the distance, was the local Ford dealership adjacent to the newly arrived stretch of the Long Island Expressway rolling eastward. What an amazing view!

What I didn’t know at the time was that our maple tree, and all the other trees in the neighborhood, village, towns and parks, were actually working to try to protect me and my young lungs from the exhaust pollution spewing from the (pre-catalytic converter) automobiles riding on that congested transportation artery.

Hold that carbon

Trees are “carbon sinks,” storehouses of carbon. Simply put, they take carbon dioxide from the air, water from the ground, and light from the sun to make glucose while releasing oxygen. The carbon is “sequestered” in trees as they incorporate it into their tissues – and grow. (See photosynthesis.)

Trees are key to reducing greenhouse gases

Assessing just how much carbon the world’s forests absorb each year is complicated. Estimates vary from 20% to as much as 40% of the carbon produced by the two main activities that cause global warming – the burning of fossil-fuels and deforestation. Whatever the percentage, nothing takes carbon from our atmosphere as efficiently as a tree. Nothing releases oxygen into our atmosphere like a tree. Clearly, we need more trees and we need to protect the ones we have so they can protect us and the habitats they engender.

Decline of forests

Unfortunately, natural forests are in decline worldwide. According to the United Nations, deforestation and forest degradation – chiefly, clearing land for agriculture – contribute to 17 per cent of the world’s carbon emissions. When forests are cleared, we not only lose ongoing carbon absorption, but whatever carbon has been stored in the soil and in those trees is eventually released into the atmosphere.

Impact of extreme weather

But it gets more complicated. The global rise in CO2 has caused more extreme weather patterns. In California, for example, the severe-drought-fire-rainfall-erosion cycle has become more pronounced each year. More frequent and higher intensity hurricanes have damaged swaths of important forests, as when Hurricane Maria hit Puerto Rico last September. As average winter temperatures rise, forests become more susceptible to infestation by the insects that now survive those warmer winters, as in parts of Colorado and Wyoming where the pine beetle has devastated forests of lodgepole pines. In times of drought, dead trees can become fuel for more fires which release stored carbon into the atmosphere.

Recovery and re-growth

Forests can and do recover, but re-growth takes time – and time is of the essence in reducing carbon in our atmosphere. Younger forests of smaller trees absorb and store less carbon. And as the climate changes, species that thrived in an area over many years may not find the same accommodating environment when they begin again. Other species may take over, with as yet unknown effects on these ecosystems. Research and adaptability will be key to understanding how to proceed.

Forest management is vital

Preserving and nurturing natural forests is of the utmost urgency if we are to get ahead of carbon release. One program that might hold promise as a way to slow deforestation in some parts of the world – and thereby delay carbon release – is a United Nations program, tested in Uganda, known as REDD Plus – “reducing emissions from deforestation and forest degradation.” This entailed paying landowners not to cut the trees on their land. Over two years, forest cover declined only 4.2 per cent in villages that had some participation, as compared to a 9.1 per cent drop in the control villages.

New trees

Planting new trees and whole forests is vital to dealing with carbon sequestration. Last year, as part of its commitment to the Paris Agreement, India planted 66 million trees in 12 hours, an amazing feat. Third in the world in CO2 release behind China and the US, India beat its own world record of planting 49 million trees in 24 hours in 2016. But accomplishing these feats required help from over one million people, a resource that not many countries affected by deforestation would be able to muster.

Technology may help

Areas that are hospitable to growing or re-growing trees are not always as easily accessible as those planted in the efforts in India. One approach to identifying and reaching ideal places to plant trees involves the use of drones which might be able to plant seeds for as many as 100 thousand trees per day, even in remote regions.

Buying time

Trees alone will not get us ahead of carbon release. But they can buy us time, absorbing and storing carbon for decades to come while we implement strategies, technologies, and regulations that reduce the amount of carbon we’re producing every day, and thereby slowing worldwide temperature rise now and for future generations.